This application claims priority of Japanese Application Nos. 332252/2000 filed Oct. 31, 2000, the complete disclosure of which is hereby incorporated by reference.
The present invention relates to a method for cutting a biological sample and to a device used therefor. More specifically, the present invention relates to a method for cutting a target area of a biological sample by irradiating the biological sample with a light beam, and a device used therefor.
A microarray technique involves hybridizing DNAs spotted on a glass slide with labelled probes prepared from RNA extracted from tissues or cells to be examined, detecting the generated signal, and then measuring the intensity of the signal to determine relative expression levels of genes corresponding to the hybridized spots. Advances in the development of such a microarray technique enable us to assay numerous genes (several thousands to several tens of thousands of genes) at a time for their expression levels. This technique can be used to exhaustively examine a disease associated with multiple abnormal genes, such as cancer or leukemia in order to identify a gene or genes abnormally expressed in such diseases. In a study aimed at determining a cause and a development mechanism of such diseases, it is important to extract only a specific type of cell from a biological sample.
For example, in molecular studies of human tumors, a quantitative or qualitative evaluation of the expression of a protein or nucleic acid in human tumor cells is necessary. In these studies, it is necessary that tumor cells are distinguished and separated from normal cells, and the expression levels of a target nucleic acid or protein are analyzed and compared in each type of the cells.
However, invasive tumor tissues contain many types of cells (e.g., tumor cells, stroma cells, endothelial cells, normal epithelial cells and inflammatory cells). In order to accurately perform a quantitative or qualitative evaluation on the expression of a protein or nucleic acid in tumor cells, it is necessary that only tumor cells are collected from many types of cells contained in tumor tissues. To this end, it is necessary that a biological sample is cut at a target position.
As a method for cutting a biological sample (e.g., living tissue fragments, cells, chromosomes and microorganisms) at a target position and collecting the cut sample, a method of irradiating laser beam on a sample for cutting and collecting the sample is known (laser capture microdissection; Emmert-Buck, M. R. et al., Science 274, 998-1001, 1996 and Bonner, R. R. et al., Science, 278, 1481-1482, 1997). This method involves adhering a biological sample to a film, cutting out a target area of the sample, and then peeling off the film to collect the fragment which was cut out. However, such a conventional method presents a problem of difficulty in operation, in particular, difficulty in locating a film on a support, due to a low film thickness. Also, the conventional method should be improved to give a better cutting (i.e., better sharpness) in cutting by a laser beam.
An object of the present invention is to provide a novel method for cutting out a target area of a biological sample (e.g., living tissue fragments, cells, chromosomes and microorganisms) and collecting the cut sample. That is, an object of the present invention is to provide a method which comprises adhering a biological sample to a film, cutting out a target area of the sample, and then peeling off the film to collect the fragment which was cut out, wherein the operability is good and a cutting sharpness in cutting by a laser beam is good.
As a result of diligent efforts to achieve the above object, the present inventors have found that a superior method for cutting a biological sample at a target position, which achieves the above-mentioned objects, can be provided by using a colored film having a thickness of 3 to 6 xcexcm to which the biological sample is adhered. The present invention was completed based on this finding.
Thus, according to the present invention, there is provided a method for cutting a biological sample by light irradiation, which comprises locating the biological sample and a colored film having a thickness of 3 to 6 xcexcm onto one side of a support, and irradiating the biological sample with a light beam, thereby cutting out a target area of the biological sample.
The present invention also relates to a method for cutting and collecting a biological sample, which further comprises collecting the sample which was cut.
According to another aspect of the present invention, there is provided a device for cutting a biological sample, wherein a colored film having a thickness of 3 to 6 xcexcm is located on one side of a support.